Hillary Clinton cites Engagement Labs’ word-of-mouth data in making the central claim of her new book, What Happened. The book, which debuted at number one on the New York Times best seller list, concerns her shocking loss to Donald Trump in the 2016 Presidential election.

Secretary Clinton quotes Engagement Labs’ offline word-of-mouth analysis, which strongly indicates that the October 28 letter to Congress from FBI Director James Comey was “first and most importantly” the factor that caused many voters to turn away from her late in the campaign.

Our Chief Commercial Officer, Brad Fay, wrote about the impact of the Comey letter on voter sentiment in a March 6, 2017, column in theHuffington Post. Our analysis noted a very late swing in sentiment toward Donald Trump, commencing at just the time of the Comey letter. Secretary Clinton writes on page 404 of her book, “According to Brad Fay of Engagement Labs, which applies well-established consumer research techniques to study elections, ‘The change in word-of-mouth favorability metric was stunning.’”

The shift in sentiment regarding Trump and Clinton supports the idea that public word-of-mouth is a key predictor of future behavior, a theme we’ve been writing about recently and one that will be the subject of new research and analysis in the near future.